Anchoring systems for securing medical devices within the cranium of a human patient have been previously described. Frequently, the device is a neurostimulator and the anchoring system is a ferrule which is affixed within the cranium in a region that has been surgically prepared by removal of a sufficient area of the skull. The ferrule is fastened to the skull using screws or an epoxy resin such as polymethylmethacrylate. The ferrule allows the neurostimulator to be situated within the cranium so that it is flush with, or slightly extruding above, the skull. Cranial placement is advantageous over implanting the neurostimulator in the body of the patient since shorter leads can be used which do not have to ascend along the neck, and which are therefore not prone to the same risk of breaking, kinking, or post-surgical migration from their intended position.
Known ferrules lack sensing and stimulating functionality, and are primarily designed for receiving and securing a neurostimulator within the skull. They may be shaped according to the individual contours of a patient's cranium and can be somewhat flexibly modified to adapt to the geometry of the surgically created region that is intended to receive the stimulation device. Cranial ferrules, when rigid, typically also provide the benefit of preventing the neurostimulator from insulting brain tissue as might occur due to an external force being applied to the device. Ferrules usually provide four or more points for securing attachment in order to minimize accidental dislocation of the device from the skull and one or more points for securing the device within the ferrule. Known ferrule devices also generally facilitate periodic removal and/or replacement of the device as may be required in order to replace a battery.
Accordingly, it would be desirable to have ferrules capable of sensing from neural tissues. It would also be desirable to have ferrules that are capable of stimulating neural tissues. Similarly, it would be desirable to have ferrules that employ their sensing and stimulating functions to detect and/or treat neurological conditions.